If a sensor is embedded in a semiconductor, the sensor experiences the same voltage as the semiconductor. For example, a temperature sensor embedded in a low-side IGBT (with a voltage over ground) can be monitored by a ground-referenced circuit. However, monitoring a temperature sensor embedded in a high-side IGBT requires a circuit with a reference potential at the emitter voltage of this high-side IGBT.
To forward the high-side analog temperature signal to a central circuit which has a reference to ground, e.g., a microcontroller or a digital signaling processor (DSP), the temperature signal is processed in a galvanically isolated manner, e.g., digitized and processed by an optocoupler or a pulse transformer. This is a costly measure which requires additional components and space. This effect becomes even more apparent in case multiple half bridges, i.e. a lot of high-side and low-side semiconductors are used, each (also the high-side switches) having a temperature sensor that should be subject to monitoring.
As an option, an analog-to-digital converter may be incorporated in a driver, e.g., a driver integrated circuit, e.g., a coreless transformer. In such scenario, an analog temperature signal can be digitized by the driver, processed (e.g., by some sort of protocol) and transmitted via the coreless transformer to the processing device (which may operate with ground as reference potential). The processing device than extracts the received temperature information for further processing purposes.